What is anaerobic threshold?

Anaerobic threshold (also called lactate threshold) is the exercise intensity at which blood lactate begins accumulating faster than your body can clear it. Below this point, you are in steady-state aerobic exercise. Above it, fatigue accelerates rapidly. It is the single most important physiological marker for endurance training.

How is threshold heart rate estimated?

A common approximation is 88% of maximum heart rate, or 85% of heart rate reserve (Karvonen). For more accuracy, lab tests measure blood lactate during a graded exercise test. Field tests like a 30-minute time trial can also estimate threshold HR — average HR over the final 20 minutes is a good proxy.

How do I train at threshold?

Tempo runs of 20-40 minutes at threshold pace, or longer interval sessions like 4 × 8 minutes with short recoveries, are classic threshold workouts. Done 1-2 times per week, they raise your sustainable pace and improve lactate clearance.

Is threshold the same as VO2 max?

No. VO2 max is your maximum aerobic capacity — the ceiling. Threshold is the percentage of that ceiling you can sustain. Two runners with the same VO2 max can have very different threshold paces. Threshold is more trainable than VO2 max in adults, which is why it is a better focus for endurance improvement.

Can I estimate threshold pace from a recent race?

Yes. 10K race pace + ~5 sec/km is a reasonable threshold pace estimate for most runners. Half-marathon pace − ~5 sec/km also works. This calculator uses 10K time when provided to estimate both threshold HR and pace.

Anaerobic / Lactate Threshold

Estimate the maximum effort sustainable for ~60 minutes — the workhorse intensity for endurance training.

Calculator

Why Threshold Matters

Endurance performance is governed by three things: VO2 max, lactate threshold, and economy. Of those, threshold is the most trainable. Improving your threshold pace by 10 seconds per km can translate to several minutes off a half-marathon time. It is the single biggest lever for endurance improvement.

How to Use the Estimate

Use the threshold HR to set your tempo zone in workouts. Aim for sessions where average HR sits within ±3 bpm of threshold. Use the threshold pace as your target for tempo runs and longer interval sets. Re-test every 6-8 weeks as fitness improves.

Formula

Threshold HR ≈ 0.88 × Max HR (or 0.85 × HRR via Karvonen)

Threshold Pace ≈ 10K race pace + ~5 sec/km

Medical Disclaimer

These estimates are population averages. For precise threshold values, lab-based lactate testing or a properly executed field test will give a personalized result.

Anaerobic / Lactate Threshold

Why Threshold Matters

How to Use the Estimate

Formula

Medical Disclaimer

Frequently Asked Questions

Related Calculators

Track Your Lactate Threshold Over Time